International Roaming (IR) refers to that a mobile subscriber who has subscribed in a Public Land Mobile Network (PLMN) of an operator in a country or region can have an access to the same mobile communication service in another country or region as in the network of the home operator. The international roaming is allowed only between countries or regions with compatibility of network systems and a bilateral roaming agreement.
In order to facilitate development of the international roaming, the International Roaming Expert Group (IREG) has been established in the International Telecom Union to build standard protocols of a signaling test, an accounting test, etc. Generally the signaling test is referred to as an IREG test and the accounting test is referred to as a Transferred Account Data Interchange Group (TADIG) test. The IREG has built relevant specifications for a guaranteed international roaming capability while proposing a sample of a quality of service that shall be offered to a mobile subscriber roaming from a network of a local operator to that of another operator. The international roaming involves aspects of, for example, a communication link (signaling and traffic) solution, an accounting data transferring solution, an international roaming fee and settlement solution, etc., for each of which an operator is required to offer significant investment, technical supports and accompanying capital and traffic management measures.
In order to provide a mobile subscriber with a high-quality international roaming service, an operator has to cooperate with another operator to set up bilateral roaming and be responsible for network software and hardware reconstruction and maintenance. The bilateral roaming is long-term and complex, and involves major issues including negotiating about a bilateral roaming agreement between the operators, IREG and TADIG tests for both of the roaming parties, signaling site lease and signaling forwarding, a settlement center design and a settlement flow, etc. A less powerful operator usually has insufficient other operators to sign bilateral roaming agreements with, so that a limited number of roaming areas are accessible to mobile subscribers who have subscribed in a network of the less powerful operator, thus restricting a demand of these mobile subscribers for the international roaming and frustrating an experience of the subscribers; and for the operator, the setting up of the international roaming through achieving a bilateral roaming agreement with another operator is time-consuming and involves issues of cross tests and signaling routing between various parties, which may hinder rapid spreading of a coverage area of the international roaming for the operator and consequently hinder an increase of its revenue on the international roaming.